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Originally published in Seasonal Guide, June 27, 2013
Let's Explore!
Tide pool fun

The Peninsula's Tide Pools

Tide pools are natural aquariums of the sea.

Photo courtesy of Marnie Davis

by Jessica Brophy

A tide pool is a special place where the ocean water stays in a pool when the tide goes out. Some tidal pools are very small—just a few inches across. Others can be quite large.

However big they are, tidal pools offer a special home to sea creatures and plants. It’s not an easy place to survive, according to a Gulf of Maine Research Institute website on tidal pools.

“Tides, temperature, saltiness—all these are constantly changing. Only hardy animals can survive in the tidepool,” the site said. “Each retreat of the tides reveals a miniature ocean world.”

So let’s have a look at what we might find in a tidal pool along the shore.

Periwinkles

Periwinkles are small sea snails. Often they are brown in color, but not always. They stick to rocks and eat algae. When you pick up a periwinkle, the animal often hides inside the shell for safety. Periwinkles must stay wet to survive, so be sure to place them back into the water if you pick one up.

Starfish

There are many different kinds of starfish, but the ones you’re most likely to find along the shores of Maine are Northern Sea Stars, which are usually orange, yellow or pink in color. Starfish usually have five arms, and if they lose an arm in a fight with a predator, most starfish can regenerate that arm. On the bottom of the starfish, where all the arms meet, you’ll find the starfish’s mouth. Starfish eat clams, mussels and oysters.

Barnacles

Those sharp, white growths on the side of the rock are not part of the rock—they’re an animal! Barnacles attach to rocks and stay, living inside their hard white shell. They then stick out tiny, fuzzy stalks to draw in plankton (tiny organisms in the water) for food. Barnacles can very easily hurt your feet; wear sandals or sneakers when walking over barnacled rocks.

Sand dollars and sea urchins

Sea urchins are small, spiky, round animals. In this area, they are a dark green color, and can hurt very much if you step on them, so be careful! Sand dollars are a species of flattened sea urchins and are typically a dark brown or dark purple as well, though the skeleton of a sand dollar will turn white. Sand dollars are sometimes called “pansy shell” because they look a bit like flowers.

Green crabs

Often juvenile green crabs can be found in tidal pools. Check underneath seaweed to find them (and hold them carefully, their claws will pinch). When the crabs grow up they are typically 3.5 inches across the carapace (the crab’s body). Crabs feed on mollusks, worms and other small sea creatures.

Don’t forget to take care to leave the tidal pools as you found them!